Lensless Scheme for Measuring Laser Aberrations Based on Computer-Generated Holograms

Abstract

All of the existing holographic wavefront sensors are either bulky or have low accuracy of measuring wavefront aberrations. In this paper, we present an improvement of the holographic method of measuring wavefront aberrations using computer-generated Fourier holograms. The novelty of this work lies in the proposed approach to the synthesis of Fourier holograms, which are implemented using phase-only SLM. The main advantages of this method are the increased diffraction efficiency compared to the previously known methods, and the more compact implementation scheme due to the elimination of the conventional Fourier-lens. The efficiency of the proposed method was confirmed by numerical simulation and optical experiments.

Breaking of Wavelength-Dependence in Holographic Wavefront Sensors Using Spatial-Spectral Filtering

“…This kind of redistribution of energy between diffraction orders in the Fraunhofer diffraction pattern can be achieved using a phase hologram [ 23 , 27 ], whose phase argument can be described by a similar equation where is a spatial phase shift produced by aberration, which is independent from λ . It can be presented as: where is the set of Zernike coefficients, and is the Zernike polynomials that have been first defined in polar coordinates and then converted into Cartesian coordinates using well-known techniques [ 28 ].…”

Computational Method for Wavefront Sensing Based on Transport-of-Intensity Equation

“…There is a compact device for measuring the wavefront based on highly efficient computer-generated holograms (CGH) in addition to traditional wavefront sensors [41,42]. The dimensions and resolution of the modulator used to output the CGH in such devices would determine the maximum spatial frequency of the CGH.…”

Reconstructing the Spatial Parameters of a Laser Beam Using the Transport-of-Intensity Equation

“…When characterizing conditionally static wave fields of light beams, their complex amplitude is usually represented in the form of two related components-amplitude (intensity) and phase distributions. A reliable estimation of the phase component of the field, often referred to as wavefront reconstruction [1][2][3] or a measurement of its aberrations [4,5], is usually the most difficult procedure. This is because one has to face problems of a possible ambiguity of the phase reconstruction [6], the presence of singular regions [7], a search for optimal boundary conditions [8] and limitations on the admissible dynamic range of phase gradients [9], which is typical for a particular measuring instrument.…”